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Biomedical subjects

J G Edwards

Publications and source records attributed to J G Edwards.

At least 19 recordsLinked to original sources
PubMed1979

Dependency upon salbutamol inhalers.

A case of dependency on salbutamol inhalers has been described. This has been discussed in relation to abuse of other drugs by alveolar absorption and other effects of salbutamol. It is not known whether the dependency is due to the salbutamol itself or to the fluorinated hydrocarbons used as propellants.

Adult↗
PubMed1979

On the reduced intercellular adhesiveness of virally transformed BHK21 cells.

Baby hamster kidney fibroblasts (BHK21 cells) transformed by polyoma or Rous sarcoma viruses aggregate less than the untransformed parental cells when incubated in growth medium in a gyratory shaker for 18-24 h. This difference can be measured by electronic particle counting, or by filtering aggregated suspensions of 32P-labelled cells through bolting fabric. The aggregation of transformed derivatives is not enhanced by the presence, during aggregation of epsilon-amino caproic acid, an inhibitor of plasmin activation. Some lines of transformed BHK21 cells do not appear less adhesive than untransformed cells in a short-term aggregation assay, and none adheres markedly less well when seeded onto homotypic cell sheets. The decreased aggregation of transformed cells is consistent with suggestions that LETS protein is involved in intercellular adhesion of fibroblasts as well as in attachment of cells to non-cellular substrates. If so, the short-term aggregation of freshly trypsinized cells may depend on secretion of LETS from an intracellular pool.

Aminocaproates↗
PubMed1978

Non-reciprocal contact inhibition of locomotion of chick embryonic choroid fibroblasts by pigmented retina epithelial cells.

Using light and electron microscopy, we have confirmed an earlier observation that chick embryonic pigmented retina epithelial cells (PRE cells) seeded in vitro on cultured sheets of choroid fibroblasts, are able to spread. Spreading is as rapid (and shows the same dependence on lateral contact between PRE cells) as on a serum-coated culture substrate. After 1 h most cells are spreading on the upper surface of the choroid sheet, but after 4 h, some PRE cells can be found sandwiched between overlapping choroid cells, and thus have invaded the sheet. Choroid fibroblasts underlie PRE in vivo, but the ability of PRE cells to spread on cultured fibroblasts is not specific for choroid, since PRE cells spread also on BKH21 hamster kidney fibroblasts, and on fibroblasts from chick embryonic heart. As reported by others for various fibroblastic cells, choroid cells seeded on to choroid sheets or on to cultured PRE are unable to spread. A possible explanation is that spreading of adherent cells is contact-inhibited by the cells in the sheet, just as their leading edges are paralysed on contact, and thus locomotion is inhibited, when fibroblasts collide on a plane substratum. If spreading of seeded cells and cell locomotion are inhibited by the same mechanism, PRE cells should contact-inhibit choroid fibroblasts with which they collide, but not themselves be so inhibited. Using time-lapse cinemicrography, we have found this to be the case. We first established that in homotypic collisions, choroid fibroblasts do show contact inhibition of locomotion, despite the criss-cross (not well monolayered) appearance of confluent cultures. In heterotypic collisions between choroid and PRE we found the predicted nonreciprocal behaviour: the choroid leading edge is paralysed on collision, and the cell subsequently retracts, whereas the active PRE margin appears to be completely unaffected. Speed measurements from a series of such collisions show that the speed of choroid cells is markedly reduced on collision with PRE, whereas the slight slowing of PRE is not statistically significant. We have observed similar behaviour in heterotypic collisions between various epithelial and fibroblastic cells, and so it seems possible that non-reciprocity may prove general for this interaction. If so, it has important implications for the role of contact inhibition of locomotion in phenomena such as morphogenesis, wound healing and the invasiveness of carcinoma cells. On the one hand, non-reciprocal contact-inhibition of locomotion may permit the spreading of epithelia over mesenchymal cells, thus generating or restoring an epithelial bounding membrane. On the other hand, in the absence of other interactions, it would fail to inhibit the invasion of mesenchymal territory by aberrant epithelial cells, or presumably by epithelial free edges.

Animals↗
PubMed1977

The diastema, the frenum, the frenectomy: a clinical study.

1. The pretreatment relationship between a clinically "abnormal"-appearing maxillary midline frenum and a midline diastema showed a strong, but not absolute, correlation. A certain percentage of patients demonstrated (1) a diastema but not an "abnormal" frenum or (2) no diastema but an "abnormal" frenum. 2. Diastema cases in which there were "abnormal" pretreatment frenums demonstrated a decidedly stronger potential for relapse after orthodontic closure. The exceptions to the rule were explained by the clinician's inability to differentiate between "normal" and "abnormal" frenums and by the periodontium's apparent (if not consistent) ability to recognize the frenal and interdental tissues following orthodontic tooth movement. 3. A three-stage surgical procedure was shown to be very effective in alleviating the relapse phenomenon following orthodontic treatment of diastemas. The surgical procedures were successful in avoiding many of the hazards to the periodontium associated with previous techniques.

Child↗
PubMed1977

Adhesive selectivity is exhibited in vitro by cells from adjacent tissues of the embryonic chick retina.

Cells from anatomically remote organs of developing embryos do not normally encounter one another. If intercellular adhesive selectivity has a role in determining or maintaining the position of cells in organs, it should be exhibited between cells which are found in close proximity within a single organ. To test this hypothesis, a collecting cell-sheet assay for intercellular adhesive selectivity has been applied to cells from 3 layers of the retina of the embryonic chick. The finding of a modest degree of selectivity of adhesion between cells from the neural retina and choroid supports the hypothesis. The observed selective low adhesiveness for self of the upper surface of pigmented retina epithelium emphasizes the likely morphogenetic significance of the topographical distribution of intercellular adhesiveness.

Animals↗